Voltage converter



Sept. 23, 1941. BOUWERS 2,256,859

VOLTAGE CONVERTER Q Filed May 26, 1939 2 Sheets-Sheet l Sept. 23, 1941. A. BOUWERS 2,256,859

VOLTAGE CONVERTER Filed May 26, 1,939 2 Sheets-Sheet 2 Patented Sept. 23, 1941 VOLTAGE CONVERTER Albert Bouwers, Eindhoven, Netherlands, assignor, by mesne assignments, to Hartford National Bank and Trust Company, Hartford,

001111., as trustee Application May 26, 1939, Serial No. 276,013 In Germany May 3-1, 1938 5 Claims.

The present invention, which is a continuationin-part of my copending U. S. patent application Ser. No. 245,514 filed December 13, 1938, now Patent No. 2,219,292, relates to a device for conconverting a direct voltage into an alternating voltage of lower value.

In transmitting electric energy over long disstances it is desirable to use direct current of a high voltage, for instance 500,000 volts, because the transmission losses are lower than when A. C. is transmitted. At the load, the D. C. must be converted into A. C. of the desired value and in my above-mentioned application I have described a converter for this purpose. More particularly, I have proposed to connect between the terminals of the direct-voltage supply, a plurality of seriesconnected controlled discharge paths, preferably grid-controlled gaseous discharge tubes, and to shunt each two successive discharge paths by a condenser. The direct-voltage supply has one terminal directly connected to one end of this series connection and its other terminal connected to a load resistance which is connected in series with a condenser across the discharge path at the other end of the series connection. Furthermore, I control the discharge paths so that only all the odd paths or all the even paths are conductive at the same time.

The main object of the present invention is to increase the amount of power which can be transmitted with such converters while using the same parts, except for the load resistance.

In accordance with the present invention I use two circuit arrangements of the above type and a common load resistance. The load resistance has a point connected to a conductor, which is prefer-ably grounded, and which is connected to a suitably chosen point of the direct voltage supply source, said point having a potential between the potentials of the supply conductors. Said load resistance has one end constructed to one end of each of the series connections of the two circuit arrangements. The free ends of the series connections are each connected to one of the D. C. supply conductors.

In order that the invention may be clearly understood and readily carried into eifect, I shall describe the same in more detail in comparison with the prior art and with reference to the accompanying drawings in which:

Figure 1 is a schematic diagram of a converter according to my above-mentioned application, and

Figure 2 is a schematic diagramv of a converter according to the present invention.

In the prior art arrangement illustrated in Figure 1, the reference numerals l9 and 2'9 designate supply lines between which a direct voltage E is applied. Connected in series and in like manner between lines l9 and 28 are four dincharge tubes l, 2, 3 and 4, shown as gaseous discharge tubes having control grids. Condensers 5, i3 and l are connected across tubes l-2, 2-3 and 3-4 respectively. Connected across discharge tube i is a series connection of a con denser 8 and a load resistance 5?, shown as the primary winding f a transformer having a secondary winding 2! across which a load is connected. However, the term load resistance as used herein and in the claims is to be understood to mean an impedance from which the load voltage is obtained and may comprise a resistance or a coil.

The tubes l t 4 are controlled in such a manner that the discharge paths of the odd-numbered tubes l and 3 are conductive when the discharge paths of the even-numbered tubes 2 and 4 are conductive, and Vice versa. As a result, condensers 5 to 8 are alternately charged and discharged and there is produced across the load resistance 9, an alternating voltage whose value depends upon the number of stages used. A suitable means for controlling the conductivity of the discharge paths of the tubes is shown and comprises a grid transformer it having a primary winding Al connected to a suitable source of alternating current 5? and a secondary winding 52 having one end connected to cathode f tube 4 and its other end connected through the parallel connection of a grid condenser and a leak resistance 54 to the grid of tube 5. Tubes i, 2 and are provided with similar grid circuits including the secondary and 45 respectively of grid transformers 5%, id and 48. The arrangement is such that the phase of the alternating current grid voltage of each succeeding tube is opposite with respect to the alternating current grid voltage of the preceding tube and for this purpose the primary winding of each of the transformers 48, ts and 56 is energized from a secondary winding on the preceding transformer. More particularly, the primary winding 5! f transformer 5% is connected to the secondary winding 52 of transformer it, the primary winding 53 of transformer G9 is connected to a secondary winding 5d of transformer and the primary winding 55 of transformer ii; is con nected to a secondary winding 53 of the transformer iii.

The grid-condensers bridged by the leak resistances are charged through the grids of the tubes during the positive phase and are discharged through the leak resistances during the negative phase. Consequently, the grids of all the tubes are negative somewhat longer than they are positive so that all the grids are negative for a short time and short circuiting of the direct current supply E is prevented.

ihe system shown in Fig. 2, which embodies the present invention, comprises two circuit arrangements A and B which are similar to that illustrated in Figure 1, and a common load resistance l8, shown as the primary winding of a transformer having a secondary winding across which a load is connected.

The circuit arrangement A comprises two gridcontrolled discharge tubes I5 and [6 connected in the same manner in series between the positive conductor 19 and terminals 23 of the load resistance Hi, a condenser I! connected across the series connection of tubes 55 and I6, and a condenser [2 connected across the series connection of tube It and load resistance H). Similarly, the circuit arrangement B comprises two grid-controlled discharge tubes I! and 18 con nected in the same manner in series between the negative conductor 28 and terminal 23, a condenser [4 connected across the series connection of tubes I? and i8, and a condenser !3 connected across the series connection of load resistance I8 and tube ii.

To control the conductivity of the discharge paths of tubes :5 to 8, a known arrangement may be provided, for instance as has been described in my copending U. S. patent application Ser. No. 245,514, and in connection with Figure 1.

Only one half the direct voltage E is applied to each of the circuit arrangements A and B and consequently the number of stages in each of the arrangements can be smaller by a factor 2 than the number of the stages in the prior art arrangement shown in Figure 1. On the other hand, the current passing through the load resistance I is twice that which passes through the load resistance 9 of Figure 1.

If the discharge path of both of the odd-numbered tubes l and I7 are conductive and at the same time the discharge paths of both of the even-numbered tubes 16 and 18 are non-conductive, the charging current of condenser [2 as well as the discharge current of condenser l3 will pass through the load resistance I9. The path of the charging current of condenser 12 can be traced from the positive line [9 through tube l5, condenser l2 and load resistance It to ground, and path of the discharge current of condenser !3 can be traced from one terminal of condenser :3 through the load resistance [0 and tube 17. This current, which passes to the left through the load resistance Ed, has twice the value of the current passed through load resistance 9 of Figure 1.

If, after a certain time interval, the discharge paths of the odd-numbered tubes and I! are blocked and at the same time the discharge paths of the even-numbered tubes 6 and I8 are made conductive, the discharge current of tube [2 as well as the charging current of condenser l3 flows to the right through the load resistance la. The path of the discharge current of condenser l 2 may be traced from condenser !2 through tube 56 and load resistance H3, and the path of the charging current of condenser 53 may be traced from ground through load resistance 10, condenser l3, and tube Hi to the negative conductor 20. Thus, the load resistance [0 must be capable of handling twice the current handled by the load resistance 9 of Fig. 1. On the other hand the power delivered to the load in Figure 2 is twice that delivered in Figure 1, while using the same supply voltage E.

In an arrangement such as shown in Figure 2, the producer of the high direct voltage must, of course, be provided with a zero point which is connected to terminal 23 or terminal 28. As shown, the high direct voltage E is produced by two generators 24 and 25 whose interconnection 21 is connected to terminal 23 by a conductor 26. In this case an alternating current of a value equal to one-half of the current passing through load resistance l0, flows through the ground. Instead of using conductor 26, terminal 23 and point 29 may, of course, be grounded.

If, instead of terminal 23, the terminal 28 of the load resistance iii is connected to point 21, either through a conductor or ground, the current passing through load resistance I0 is reduced by half, but the charging potentials of condensers l2 and !3 are lost.

The condensers 5, II and I2 may be omitted without modifying the voltages, current strengths or the operation of the arrangements illustrated in Figures 1 and 2. However, if this were done, the device shown in Figure 2 would have the further advantage over the device of Figure 1 that one less condenser is used.

In the arrangement shown, the peak value of the alternating voltage obtained across the load resistance l 9 is less than the voltage E by a factor 4. However, by using additional stages, this voltage can be further increased by factors of 6, 8, 10 etc.

I have shown a single-phase transformer as the load resistance but a multi-phase transformer, for instance a three-phase, may be used. In such a case, however, the load resistance It! would in each instance, consist of one of the three primary windings whose star point would be grounded. This has been shown in Figure 3. By a corresponding phase displacement in the control of the discharge paths of the tubes, a three-phase cur rent could be produced.

In Figure 3 conductor l9 has been connected through the circuits C, D and E with the point 23, so that three closed circuits are formed via conductor 26, terminal 21 and generator 24. Similarly three closed circuits are formed beginning at conductor 28, the circuits F, G and H, terminal 23, conductor 25, terminal 27, and sonerator 25. The windings 29, 30 and SI are shown as to be the primary windings of a three phase transformer, which secondary windings output are numbered with 32, 33 and 34. The discharge tubes and the condensers shown in each of the circuits, CH, DG or EF are similarly connected in the circuits as described in Figure 2.

While I have described my invention in connection with specific applications and details of construction, I do not wish to be limited thereto because obvious modifications will present themselves to one skilled in the art.

What I claim is:

l. A device for converting a direct voltage of comparatively high value into an alternating voltage of lower value comprising two circuit arrangements each comprising a plurality of controlled discharge tubes connected in the same manner in a series connection, each connection having one end connected to one and the same end of a common load resistance, and a condenser connected across each two succeeding tubes and a condenser connected across the series connection of said load resistance and the discharge tube connected thereto, the other ends of the series connections being connected to the direct voltage supply conductors, a connection between a point of said load resistance and a point of the direct current supply source said point having a potential between the potentials of the supply conductors, the arrangement being such, that the discharge tubes of both circuit arrangements are connected in the same manner in a series connection and means for controlling the conductivity of the discharge paths of said tubes in such a manner that periodically all the even-numbered tubes are made conductive, while at the same time all the odd-numbered tubes are made non-conductive and vice versa.

2. A device for converting a direct voltage of comparatively high value into an alternating voltage of lower value comprising two circuit arrangements each comprising the same number of controlled discharge tubes connected in the same manner in a series connection, each connection having one end connected to one and the same end of a common load resistance, and a condenser connected across each two succeeding tubes and a condenser connected across the series connection of said load resistance and the adjacent discharge tube, the

other ends of the series connections being connected to the direct voltage supply conductors, a connection between one end of said load resistance and a zero-point of the direct-voltage supply, the arrangement being such, that the discharge tubes of both circuit arrangements are connected in the same manner in a series connection and means to control the conductivity of the discharge paths of said tubes in such a manner, that periodically all the even numbered tubes are made conductive, while at the same time all the odd-numbered tubes are made non-conductive and vice versa.

3. A device for converting a direct voltage of comparatively high value into an alternating voltage of lower value, comprising two circuit arrangements each including a plurality of controlled discharge tubes connected in the same manner in a series connection having one end connected to one and the same end of a common load resistance, a condenser connected across each two succeeding tubes and a condenser connected across the series connection of said load resistance and the discharge tube connected thereto, a controlled discharge tube connected between each of the other ends of the series connections and one of the direct voltage supply conductors, a connection between a point of said load resistance and a point of the direct current supply source, said point having a potential between the potentials of the supply conductors, the discharge tubes of both circuit arrangements being connected in the same manner in a series connection, and means for controlling the conductivity of the discharge paths of the tubes of the circuit arrangements in such a manner that periodically all the even-numbered tubes are made conductive while at the same time all the odd-numbered tubes are made nonconductive and vice versa.

4. A device for converting a direct voltage of comparatively high value into an alternating voltage of lower value, comprising a three-phase transformer having three primary windings each acting as a load resistance, three circuit arrangements each comprising two circuits each including a plurality of controlled discharge tubes connected in the same manner in a series, each of the circuits of each arrangement having one end connected to one end of one of said primary windings and its other end connected to a direct voltage supply conductor, a condenser connected across each two succeeding tubes, and a condenser connected across the series connection of the primary winding and the discharge tube connected thereto, a connection between a point of said primary windings and a point of the direct current supply source, said latter point having a potential between the potentials of the supply conductors, the arrangement being such that the discharge tubes of both circuits of each arrangement are connected in the same manner in a series connection, and means for controlling the conductivity of the discharge paths of the tubes of said circuits in such a manner that periodically all the even-numbered tubes of each arrangement are made conductive while at the same time all the odd-numbered tubes are made non-conductive and vice versa and the control of tubes of the three arrangements has a mutual phase displacement of 5. A device for converting a direct voltage of comparatively high value into an alternating voltage of lower value, comprising a three-phase transformer having three primary windings each acting as a "load resistance, three circuit arrangements each comprising two circuits each including a plurality of controlled discharge tubes connected in the same manner in a series, each of the circuits of each arrangement having one end connected to one end of one of said primary windings and its other end connected to a direct voltage supply conductor, a controlled discharge tube in said latter connection, a condenser connected across each two succeeding tubes, and a condenser connected across the series connection of the primary winding and the discharge tube connected thereto, a connection between a point of said primary windings and a point of the direct current supply source, said latter point having a potential between the potentials of the supply conductors, the arrangement being such that the discharge tubes of both circuits of each arrangement are connected in the same manner in a series connection, and means for controlling the conductivity of the discharge paths of the tubes of said circuit in such a manner that periodically all the evennumbered tubes of each arrangement are made conductive while at the same time all the oddnumbered tubes are made non-conductive and vice versa and the control of the three arrangements have a mutual phase development of 120.

ALBERT BOUWERS. 

